Water heater control system



Feb. 6, 1945.

C. M. OSTERHELD WATER HEATER CONTROL SYSTEM File Jan. 13, 1944 2 Sheets-Sheet l llllllllll/ f/ 37 W if"; 195' 39'ITI iv! '63 17 85- E E! 7/" 7 :"f C in. 5 3". 69

INVENTOR.

ATTORNEY *Feb. 6, 1945. c. M. OSTERHELD WATER HEATER CONTROL SYSTEM Filed Jan. 13] 1944 2 Sheets-Sheet 2 IN VEN TOR. y Gamma p ATTORNE Y Patented Feb. 6, 1945 ascassa WATER. HEATER CONTROL SYSTEM Clark M. Osterheld, Stoughton, Wis assignor to 'McGraw Electric Company, Elgin, 111., a corporation of Delaware Application January 13, 1944, Serial No. 518,188

1'! Claims. 4 (Cl. 219-49) My invention relates to electric heating and particularly to control systems for electric water heaters. I

An object of my invention is to provide a relatively simple system for controlling an electric heater for a domestic hot water tank that Shall be efiective to cause energization of the'heater immediately after withdrawal of a relatively large quantity of hot water from the tank and to cause energization of the heater with a predetermined time delay period in case of withdrawal of a relatively small quantity of hot water from the tank.

Another object of my invention is to provide a heater control systemeffective to cause selective energization of the electric heater immediately or with a time delay period in dependence on the amount of hot water withdrawn from a tank and that shall be effective to cause deenergization of the heater when substantially all of the water in the tank is hot.

Another object of my invention is to provide a heater control system for a hot water tank that shall be eflective to cause selective energization of the heater immediately or with a time delay period upon startin of an ofi-peak period in accordance with the amount of hot water withdrawn from a tank during the on-peak period.

In the drawings,

Figure 1 is a vertical sectional view through a water tank to which has been applied a system embodying my invention, the parts of which are in the positions they will occupy when the tank is full of hot water, 7 1

Fig. 2 is a diagram of the circuits with the contacts in the positions as when the upper portion of the tank contains hot water and the lower portion contains cold water and the timed period of the retarder switch has been completed,

Fig. 3 is a fragmentary vertical sectional view and a circuit diagram showing a modification of the system shown in Fig. 1 of the drawings, the

hot water outlet pipe IS, the tank ll being surrounded by suitable heateinsulating material ll. such as rock wool, which heat insulation may be held by an outer casing l 9, all as now well knownin the art.

I provide preferably but not necessarily, a single electric heater 2| for the tank which may be of any suitable or desired construction but is shown as being a convoluted resistor strand insulatedly clamped around the outside of the tank adja cent the lower end portion thereof and located in a tunnel 23. All of these details are now well known and used in the art.

I provide a first thermally-actuable heater cont'rol switch 25 which has been shown schematically only as comprising a bimetal bar 21 mounted in heat-conducting relation relatively to the tank water on the tank adjacent the lower end portion thereof. I may use any other thermal heater control switch effective for the same purpose.

I provide also a second heater control switch 29 which is located in heat-receiving relation relatively to the tank water intermediate the ends of the tank and I may mount it at substantially one-half the height of the tank. The thermallyactuable switch 29 includes a bimetal bar 3| conducting or heat-receiving relation relatively to the tank. The switch structure 33 includes a housing 35 which may be and preferably is made of a heat-insulating material and has been shown schematically only'in the different figures of the drawings. Within the housing or casing 35 I provide a bimetal bar 31 having one of its ends mounted against a heat-insulating support 39 while the other free end is adapted to be engaged with and be disengaged from a fixed or adjustably fixed contact 4|.

I may also include in the control system a continuously operative timer controlled circuit switch unit designated by numeral 43 and comprising an electric motor 45 having a worm 41 on its shaft engaging a worm gear 49. This worm gear is mounted on a shaft 5| which shaft also has fixed thereon a cam disc 53, the major portion of which isof the same radius but which has a smaller portion 55 having a larger radius. I have shown these parts schematically only since such devices are well known in the art, and it is to be understood that the cam disc is adapted to be rotated through one full revolution of 360 during a twenty-four hour day and that the peripheral extent of portion 55 is equal to the length of an off-peak period and further that the position of portion 55 On shaft 5| is determined by the oft-peak period, which is usually from 12 midnight to 6 a. m.

A heater circuit switch actuable by the cam disc includes a substantially rigid contact arm 51 and a resilient contact arm 59, having a lug 6|, of electric-insulating material, thereon at its free end adapted to engage the peripheral surface of cam disc 53. When the lug BI is in engagement with the on-peak portion of disc 53, the arm 53 is out of engagement with arm 51. but is moved into engagement therewith when it engages portion 55, so that the switch is in closed position during on-peak periods of a twenty-four hour day. It is to be understood that the showing of this switch is schematic only, and any device efiective for the desired p p e may be used.

Contact arm 51 is connected to one supply circuit conductor 63, while the other contact arm.

53 is connected by a conductor 35 with contact ll and with a fixed contact '67 of the second thermal switch 29. The other terminal of switch 23 is connected by a conductor 89 to one terminal of electric heater 2|, the other terminal of which is connected to the fixed end of bimetal bar 21. The fixed contact member 1| 0 switch 25 is connected by a conductor 13 to the second supply circuit conductor 75.

A conductor II connects conductor 69 with one terminal of the third thermal switch 33 and a conductor 13 connects the fixed end of himetal bar 21 and one terminal of heater 2| to one terminal of an adjustable rheostat ill, the other terminal of which is connected by a conductor 83 to one terminal of a low wattage heating coil 85, the other terminal of which is connected to contact 4|. The heating coil 85 may be mounted on and around bimetal bar 31 or in heat-transferring relation relatively thereto and is such that it will cause closure of the switch by engagement of bimetal bar 31 with fixed contact member II in an adjustably predetermined time period on the order of four to six hours.

It will be noted that the third thermal heater control switch 33 is electrically connected in shunt with the second thermal heater control switch, which latter is connected in series circuit relation with the first thermal heater control switch 25 and with the timer controlled switch 43.

Let it be assumed that the tank is filled with cold water, the temperature of which is on the order of 70 F., in which case 'bimetal bars 21 and 3| will be in engagement with contact members 1| and 51 respectively. If this occurs during an on-peak period, the timer controlled switch will be open so that energization of heater 2| will not be eflected, but will be delayed until the start of an off-peak period and closure of the timer controlled switch, when energlzation of the heater will be eflected.

Coincident with the initiation of the energization of heater 2|, energization of the heating coil' it it be assumed that the total lengthof time ry to heat all orsubstantially all of the switch 25 when substantially all of water in the tank H to a predetermined high temperature on the order of 150 F. is on the order of eight hours, and the second switch 23 is positioned at substantially the mid-portion of the tank bimetal bar 3| would be moved to open position in about eight hours since the effect of a single lower heater is to heat the water uniformly over the entire length of the tank un til the heater is deenergized by the lower thermal switch 25 when the temperature of the water has reached the desired value, say 150 F. Energization of the heater 2| will therefore continue through the lower thermal switch 25, the second thermal switch 29, and the timer controlled switch during the first four hours and through the closed third switch 33 shunting the second switch during the next four hours, or until substantially all of the water is hot or the timer controlled switch is opened. It now the adjustment of rheostat 8| was such that it would take, say, four hours to cause suflicient heating of bimetal bar 31 to cause it to flex sufllciently to engage contact member 4|, energization of the heater 2| would continue through closed switch 25, closed switch 33 and closed timer controlled switch. This energizatlon of the heater 2| would continue until interrupted either by opening of the timer controlled switch at the end of an oil-peak period or by opening of the first thermal heater control switch 25 when substantially all of the water in the tank is hot. By "hot" I refer to water having a temperature of 150 F. or slightly higher.

If the timer controlled "switch 43 is omitted, energization of electric heatei-2l will start im mediately upon filling th tank with cold water and will continue as set forth above except that deenergization 0f the heater 2| will be effected by the lower thermal switch 25 when substantially all of the water in the tank is hot.

Let it now be assumed that hot water has been withdrawn from the tank, the quantity being such that only the lower heater control switch 25 is subject to cold water and switches 29 and 33 will be in open position. 11' the timer controlled switch 43 is included in the circuit and this withdrawal occurs during an on-peak period no further change would occur until the start of an elf-peak period and closure of the timer controlled switch. Closure of switch 43 would cause energization of heatin coil through closed switches 25 and 43 with rise of temperature of bimetal bar 31 andits engagement with contact member 4| after a predetermined time period of delay. Closure of switch 33 would cause energization of heater 2|, which energization would continue until interrupted by opening of the timer controlled switch 43 at the end of an oil'- peak period or by opening of the lower thermal the water in the tank is hot.

Let it be assumed that the timer controlled switch unit is not provided and that small changes in the adjustment of the rheostat 3| are made to lengthen the time period required to heat the bimetal bar 31 to its maximum temperature or that a heating coil of lesser wattage be installed. If a small quantity of hot water was used early in the morning, say, at about '7 oclock, and assuming that the length of tim necessary to cause heating of the bimetal bar 31 is on the order of five hours, reenergization of the heater 2| wlllbe delayed until 12 o'clock noon or shortly after, which brings the reenergization period into the-early afternoon off-peak period. The same erly heat the same.

into tube I03 and bellows I05 to cause increase comments apply with regard to when a small quantity of water is withdrawn during the late afternoon hours or early evening hours, say, at

7:00 p. m. The five-hour time period of delay will cause reenergization of the heater 2I to take place at or shortly after 12:00 midnight, thus bringing the reenergization period into the'late night hours.

If, on the other hand, sufiicient hot water has been withdrawn from the tank to cause subjection of the intermediate heater control switch 29 to cold water, the switch 29 will be moved immediately to closed position thereby causing immediate energization, without any time delay period, of the heater 2I.

Referring'now to Figs. 3 and 4 of the drawings. I have there shown a modification-of certain of the thermal switches shown in Figs. 1 and 2. Identical parts of Figs. 3 and 4 with those shown in Figs. 1 and 2 have been given the same numbers. The lower thermally-actuable heater control switch 25 may be substantially the same. while the upper thermally-actuable heater control switch mounted in heat-conducting relation on the tank at substantially the mid-height there-- of may have the form of a tubular member 81 having a closed inner end, mounted on the tank I I with its outer end in'fiuid-tight manner relatively thereto.

I provide-a bellows 89, the inner end of which is secured in a fluid-tight manner to the outer endof tube 81, and I locate in the tube and the bellows a suitable vaporizable fluid which will vaporize at or substantially at the temperature of hot water which, as has been hereinbefore stated, may be on the orderiof 150 F. Bellows 89 is closed at its outer endand hasa lug 9| mounted thereon which is adapted to engage and be disengaged from a resilient contact bar 93 having one end thereof mounted on a fixed contact 95 while the other end thereof is adapted to engage and be disengaged from a fixed contact member I provide also a third thermally-actuable heater control switch designated generally by numeral 99, locatable anywhere out of close thermal communication with tank II, this switch comprising a suitable casing I M which may and preferably is made of a suitable heat-insulating material of any kind now well known in the art. I locate within the casing 99 a tubular member I03 having one open and one closed end, the open end having secured thereto in fluid-tight manner an'expansion bellows I 05 having a closed outer end all in a manner well known in the art. I provide a lug I01, of electric-insulating material, on the outer end portion of bellows I05 which is adapted to engage with and be disengaged from a resilient contact arm I09 normally out of engagement with a substantially rigid contact arm III. While I have shown lug I01 as being out of engagement with contact arm I09, this is not conductor II! with fixed terminal 91 of the second or intermediate thermally-actuable heater control switch.

Conductor II is connected by a conductor III with terminal 'II of, the lower heater control tor I2'I with conductor H5.

Substantially the same operations will occur in the system of Figs. 3 and 4 in case of first filling of tank I I with cold water as was hereinbefore set forth in connection with a system of Figs. 1 and 2 and the same comments apply to the system of Figs. 3 and 4 as were hereinbefore made in connection with the system shown in Figs. 1 and 2 when a relatively small quantity of hot water was withdrawn from the tank and when a larger quantity of hot water was withdrawn from the tank and repetition of such description is believed -to beunnecessary.

, ed to a source of supply of electric energy to cause an essential but the disengagement of contact- I arms I09 and III under normal conditions is an essential. I provide a small auxiliary heating coil I I2 which I have shown as being positioned within tube I03 although I may locate the coil II2 around the tubular member I03 in order to prop- An expansible fiuid is put .the fixed terminal of contact arm III and by a energizatlon of the heater with a predetermined time period of delay in case oiiwithdrawal of only a relatively small quantity of hot water from the tank and immediate energization of the heater in case a greater quantity of hot water is withdrawn from the tank.

In case the system includes a timer controlled switch as shown in Fig. 1, the .heater 2I will be energized immediately after closure of the timer switch if enough hot water was withdrawn to subject the intermediate switch to cold water and will be energized with an adjustably predetermined time delay period in case only enough .hot water was withdrawn to subject the lower thermal switch to cold water, thus ensuring that energization of the tank heater takes place only during off-peak periods.

Various modifications may be made in the systems embodying my invention without departing from the spirit and scope thereof and all such modifications coming clearly within the scope of the appended claims are to be considered a part of my invention.

I claim as'my invention:

l. A water heater system comprising a tan electric heating means for said tank, a first thermalIy-actuable control means for said heating 0nd control means and including a heating coil controlled by said first thermally-actuable control means, to cause energization of said electric heating means through said first and said second control means in case.said tank contains enough cold water to effect said'second control means and to cause energization of said heating means through said first and said third control means with a predetermined time delay period in case the bottom portion 01' the tank is filled with enough cold water to afiect said first control means only.

2. A water heater system comprising a tank for hot water having a cold water inlet at the bottom of the tank and a hot water outlet at the top oi the tank and subject to withdrawals of hot water during a twenty-four hour day, electric heating means for said tank, a first thermallyactuable controlling means for said heating means subject to tank water temperature at the bottom portion of the tank, a second thermallyactuable control means for said heating means subject to tank water temperature intermediate the ends of the tank, a third thermally-actuable control means for said heating means connected in parallel-circuit relation with said second control means and including a heating coil controlled by said first control means, to cause energization of said heating'means through said first and said second control means when the tank is first filled with cold water, to complete heating of all of the water in the tank through said first and said third control means and to cause deenergization of said heatin means by said first control means when all of the water in the tank is hot.

3. A water heater system comprising a tank for hot water having a cold water inlet at the bottom of the tank and a hot water outlet at the top of the tank and subiect to withdrawals of hot water during a twenty-tour hour day, electric heating means for said tank, a first thermally-actuable switch for said heating means sub ject to tank water temperature at the bottom portion of the tank, a second thermally-actuable switch for said heating means subject to tank water temperature intermediate the ends of said a tank, a third normally-open thermally-actuable switch for said heating means, a heating coil for said third switch to cause closure thereof and electric connections for connecting said first and second switches in series circuit with each other and with said heating means, for connecting said third switch in parallel circuit relation with said second switch and for connecting said heating coil to be controlled by said first switch, to cause energisation of said heating means with a predetermined period of time delay through said first and third switch in case enough hot water is drawn oil to subject said first switch to cold water andto cause deenersization of said heating means by said first switch when substantially all of the water in the tank is hot.

4. A water heater system comprising a tank for hot water having a cold water inlet at the bottom oi the tank anda hot water outlet at the top of the tank and subject to withdrawals of hot water during a twenty-tour hour day, electric heating means for said tank, a first thermally-actuable controlling means for said heating means subject to tank water temperature at the bottom portion or the tank, a second thermally-achiable control means for said heating means subject to tank water temperature intermediate the ends of the tank, a third thermallyactuable control means for said heating means connected in parallel-circuit relation with said second control means, out of close thermal communication with said tank, and including a heating coil controlled by said first control means, to cause energlzatlon of said heating means through said first and said second control means when the tank is first filled with cold water, to complete heating 01 all of the water in the tank through said first and said third control means and to cause deenergization of said heating means by said first control means when all of the water in the tank is hot.

5. A water heater control system for a tank having electric heating means, a first thermallycontrolled switch for said heating means subject to tank water temperature at the bottom portion of the tank, a second thermally-controlled switch for said heating means subject to tank water temperature at an intermediate portion of the tank and connected in series circuit with said first switch and a third thermally-controlled switch for said heating means connected in parallel circuit relation with said second switch and having a heating coil, the energization of which is controlled by said first switch, to cause closure of said third switch with an adjustably preset time period of delay 'in case said first switch is closed by cold water in the bottom portion of the tank.

6. A water heater control system for a tank having electric heating means, a first thermally-controlled switch for said heating means subject to tank water temperature at the bottom portion of the tank, a second thermally-controlled switch for said heating means subject to tank water temperature at an intermediate portion of the tank and connected in series circuit with said first switch and a third thermally-controlled switch for said heating means connected in parallel circuit relation with said second switch and including a thermally-responsive element and a heating coil therefor, the energization of said heating coil being controlled by said first therrnal switch, said first and second switches jointly causing energization of said heating means if the tank contains sufiicient cold water to affect both said first and said second switch.

'7. A water heater control system for a tank having electric heating means, a first thermallycontrolled switch for said heating means sublect to tank water temperature at the bottom portion of the tank, a second thermally-controlled switch for said heating means subject to tank water temperature at an intermediate portion. of the tank and connected in series circuit with said first switch and a third thermally-controlled switch for said heating means connected in parallel circuit relation with said second switch and including a thermally-responsive element and a. heating coil therefor, the energization of said heating coil being controlled by said first thermal switch, said first and said third switch jointly causing energization of said heating means with apreset time delay period in case the tank contains enough cold water to afiect said first thermal switch only. A

8. A water heater control system for a tank having electric heating means, a first thermallycontrolled switch for said heating means subject to tank water temperature at the bottom portl'on of the tank, a second thermally-controlled switch for said heating means subject to tank water temperature at an intermediate portion of the tank and connected in series circuit with said first switch and a third thermally-controlled switch ior said heating means connected in parallel circuit relation with said second switch and including a thermally-responsive element and a heating coil therefor, the energization of said heating coil being controlled by said first thermal switch, said first and said third switch jointly causing energimtion 0! said heating means with a preset time delay period in case the tank contains enough cold water to afiect said first thermal switch only and said first switch causing deenergization of said heating means when substantially all of the water in the tank is hot.

9. A water heating control system for a domestic hot water tank havin a cold water inlet at its bottom end, a hot water outlet at its top end, a single electric heater near its bottom end, a first thermal-control switch for said heater subject to tank water temperature near its bottom portion, a second thermal-control switch for said electric heater subject to tank water temperature inter- .mediate the ends of the tank and connected in series circuit relation with said first switch, a third thermal-control switch for said electric heater havingits contacts connected in parallel circuit relation with said second switch, an electric heating coil for said third switch connected to b controlled by said first switch, said first and said second switch being adapted to effect immediate energization of said electric heater upon filling of the tank with cold water.

10. A water heating control system for a domestic hot water tank having a cold water inlet at its bottom end, a hot water outlet at its top end, a single electric heater near it bottom end, a first thermal-control switch for said heater subject to tank water temperature near its bottom portion, a second thermal-control switch for said electric heater subject to tank water temperac ture intermediate the ends of the tank and connected in series circuit relation with said first switch, a third thermal-control switch for said electric heater having its contacts connected in parallel circuit relation with said second switch, an electric heating coil for said third switch connected to be controlled by said first switch, said first and'said second switch bein adapted to effect immediate energization of said electric heater upon filling of the tank with cold water and said first and said third switch being effective to cause energization of said electric heater with an adjustably presettime delay period in case of withdrawal of a quantity of hot water sufficient to cause said first switch to be subject to cold water. 11. A water heating control system for a domestic hot water tank having a cold water inlet at its bottom end, a hot water outlet at its top end, a single electric heater near its bottom end, a first thermal-control switch for said heater subject to tank water temperature near its bottom portion, a second thermal-control switch for said electric heater subject to tank water temperature intermediate the ends of the tank and connected in series circuit relation with said-first switch, a thirdthermal-control switch for said electric heater having its contacts connected in parallel circuit relation with said second switch,

an electric heating coil for said third switch connected to be controlled by said first switch, said first and said second switch being adapted to effect immediate energization of said electric heater upon filling of the tank with cold water and said first and said third switch being effective to cause energization of said electric heater with an adjustably preset time delay period in case of withdrawal of a quantity of hot water sufiicient to cause said first switch to be subject to cold water and said first switch effecting deenergi-v zation of said electric heater when substantially all of the water in the tank is hot.

12. A water heater control system for a domestic hot water tank subject to withdrawals of hot water therefrom during a twenty-four hour electric circuit with said first switch, a third thermal heater control switch out of close thermal communication with said tank connected in parallel circuit relation with. said second switch and an electric heating coil for said third switch controlled by'said first switch, said first and said second switch being effective to cause immediate energization of said heater incase enough hot water is withdrawn from the tank so that the first and the second switch are subject to cold water.

13. A water heater control system for a domestic hot water tank subject to withdrawals of hot water therefrom during a twenty-four hour day,

said tank having a cold water inlet at its lower end and a hot water outlet at its top end, a single electric heater near its lower end, a first thermal heater control switch subject to tank water temperature near the lower end of the tank, a second thermal heater control switch on the tank intermediate its ends connected in series electric circuit with said first switch, a third thermal heater control switch out of close thermal communication with said tank connected in parallel circuit relation with said second switch and an electric heating coil for said third switch controlled by said first switch, said first and said second switch being effective to cause immediate energization of said heater in case enough hot water is withdrawn from the tank so that the first and the second switch are subject to cold water and said first and said third switch being effective to cause energization of said heater with a preset time delay period in case enough hot water is Withdrawn from the tank so that the first switch only is subject to cold water.

14. A water heater control system for a domestic hot water tank subject to withdrawls of hot water therefrom during a twenty-four hour day, said tank having a cold water inlet at its lower end and a hot water outlet at its top end. a single electric heater near its lower end, a first thermal heater control switch subject to tank water temperature near the lower end of the tank, a second thermal heater control switch on the tank intermediate its ends connected in series electric circuit with said said first switch, a third thermal heater control switch out of close thermal communication with said tank connected in parallel circuit relation with said second switch and an electric heating coil for said third switch controlled by said first switch, said first and said second switch being effective to cause immediate energization of said heater in case enough hot water is wthdrawn from the tank so that the first and the second switch are subject to cold water and said first and said third switch being effective to cause energization of day, 'said tank having a cold water inlet at its lower end and a hot water outlet at its top end, a single electric heater near its lower end adapted to be energized from a source of supply of electric energy having a period of low demand for electric energy after midnight, a first thermal heater control switch subject to tank water temperature near the lower end of the tank, a second thermal heater control switch subject to tank water temperature intermediate the ends of the tank and connected in series circuit relation with-said first switch, a third thermal heater control switch out of close thermal communication with said tank connected in parallel circuit relation with said second switch and an electric heating coil for said third switch controlled by said first switch, said first and said third switch being jointly eflective, in case enough hot water is withdrawn irom'the tank during the early evening hours to cause said first switch to be subject to cold water, to cause energization 01 said electric heater during the period of low demand for electric energy after midnight.

16. A water heater control system for a tank having an electric heater, comprising a first thermally-controlled switch for said heater subject to tank water temperature at the bottom portion or the tank, a second thermally-controlled switch Ior said heater subject to tank water temperature intermediate the ends or the tank, connected in series circuit with said first switch, a timer controlled switch for said heater in series circuit with said first and second switches and adapted to be closed during oilpeak periods, and a third thermally-controlled switch for said heater connected in parallel circult relation with said second switch and having a heating coil, the energizatlon of which is jointly controlled by said first switch and said timer controlled switch, to cause energization of said electric heater through said first, second and timer controlled switch immediately upon closure of said timer controlled switch in case both said first and second switches are subject to cold water.

17. A water heater control system for a tank having an electric heater, comprising a first thermally-controlled switch for said heater sub' ject to tank water temperature at the bottom portion of the tank, a second thermally-controlled switch !or said heater subject to tank water temperature intermediate the ends of the tank, connected in series circuit with said first switch, a timer controlled switch for said heater in series circuit with said first and second switches and adapted to be closed during oi!- peak periods, and a third thermally-controlled switch for said heater connected in parallel circuit relation with said second switch and having a heating coil, the energization of which is jointly controlled by said first switch and said timer controlled switch, to cause energization of said electric heater through said first, second and timer controlled switch immediately upon closure of said timer controlled switch in case both said first and second switches are subject to cold water and'to cause energization of said electric heater throughsaid first, third and timer I controlled switch with a predetermined time delay period ai'ter closure of said timer controlled switch in case only said first switch is subject to cold water.

CLARKM. OSTERHELD. 

